The SPIZWURZ Project - Experimental and Modeling Approaches of Hydrogen in Cladding Tubes Under Dry Storage Conditions

Abstract When hydrogen penetrates into cladding tubes during operation of nuclear power plants, it may affect their mechanical stability. During the dry storage of spent nuclear fuel, the initially dissolved hydrogen precipitates as hydrides in the metallic matrix. This precipitation process induces a certain stress in the zirconium structure of the cladding tube. In the framework of the SPIZWURZ project, cladding tubes are charged with hydrogen and exposed to a certain pressure — either internal or external, in order to investigate the stress influence on the hydrogen diffusion and solubility under dry storage conditions. The relevant long-term bundle test that simulated dry storage conditions with a constant cooling period of 250 days has recently ended. As described in the paper, the preliminary calculations for the temperature development and the hydride state shall be compared to the real state of the bundle after the test. Therefore, various analytical methods will help to determine relevant parameters that will be used for the fuel rod performance code TESPA-ROD from the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS), which shall be revalidated in this framework.